1. Field of the Invention
This invention relates to a method and a device for medical imaging, and more specifically, calibration of the mechanical model for the behavior and movement of a radiology examination table in relation to a vascular gantry in medical imaging systems.
2. Description of Related Art
Vascular gantries are typically used in medical imaging in order to acquire: first, prior to an operation, 3-D images of a given organ; and second, in the course of the operation, 2-D fluoroscope images of the same organ.
This type of 2-D fluoroscopic image makes it possible, for example, for the surgeon to get oriented before navigating around the vascular structures, and to verify the position and deployment of his tools.
In the technique known as 3-D Augmented Fluoroscopy (3DAF), the 3-D image obtained in the course of the operation is superimposed on the 2-D image of the structure or the organ being operated on, acquired prior to the operation. The 3-D view is calculated in such a way as to give it the same viewing angle as the 2-D fluoroscopic on which it is being superimposed.
This kind of superimposing assumes whatever exact knowledge of the relative position and the distortion undergone by the table carrying the object or the patient and the vascular gantry carrying the source and the imaging system sensor.
An example of a process that allows for calculating the position and distortions undergone by the vascular gantry is described in patent application US 2007/0172033. This document describes how to calibrate the mechanical model of the vascular gantry which will then be used jointly with the system positioning sensors in order to recalibrate the relative positions of the 3-D image and the fluoroscopic images (making it possible to generate “augmented fluoroscopic images”).
However, the table's movement and the distortion it undergoes are not taken into account in this calibration method. One difficulty lies in calculating the table's parameters with regards to its movements and mechanical behavior. The greater the precision with which the table's mechanical parameters are determined, the better will be the quality of the recalibrated augmented fluoroscopic images.